Method of assembling a modular snowmobile platform

ABSTRACT

The present invention concerns a method for designing and manufacturing a snowmobile platform. The method entails designing and manufacturing a group of tunnel subassemblies, designing and manufacturing a group of engine cradle subassemblies, and designing and manufacturing a group of front suspension subassemblies. Next, one tunnel subassembly, one engine cradle subassembly, and one front suspension subassembly are selected from each respective group. Then, the tunnel subassembly is connected to the engine cradle subassembly at a rear portion thereof. Finally, the front suspension subassembly is connected to the engine cradle subassembly at a front portion thereof to create the snowmobile platform. The present invention also concerns a snowmobile platform constructed according to this method, which combines, among other elements, a tunnel subassembly, an engine cradle subassembly, and a front suspension subassembly.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/422,543, titled “MODULAR SNOWMOBILE PLATFORM”, filed Jun. 6, 2006.Through the '543 application, this application is also a division ofU.S. patent application Ser. No. 10/734,267, titled “MODULAR SNOWMOBILEPLATFORM”, filed Dec. 15, 2003. Through the '267 application, thisapplication claims the benefit of priority to U.S. Provisional PatentApplication Ser. No. 60/429,536 entitled “MODULAR SNOWMOBILE PLATFORM”which was filed on Nov. 29, 2002. This application is also related toU.S. Non-Provisional patent application Ser. No. 10/141,135, which wasfiled on May 9, 2002. This application is also related to U.S.Non-Provisional patent application Ser. No. 09/877,064, filed Jun. 11,2001, claiming priority to U.S. Provisional Patent Application Ser. No.60/246,110, filed Nov. 7, 2000. In addition, this application relates toU.S. Non-Provisional patent application Ser. No. 09/472,133, entitled“IMPROVED VEHICLE” filed on Dec. 23, 1999. That application claimspriority to Canadian Patent Application No. 2,256,944, which was filedon Dec. 23, 1998. This application also relates to U.S. Non-Provisionalpatent application Ser. No. 09/472,134, entitled “SNOWMOBILE,” which wasfiled on Dec. 23, 1999. In addition, this application relates to U.S.Provisional Patent Application Ser. No. 60/230,432, entitled “A NOVELTHREE-WHEELED VEHICLE,” which was filed on Sep. 6, 2000. Finally, thisapplication relates to U.S. Provisional Patent Application No.60/237,384, which was filed on Oct. 4, 2000. The contents of each of theapplications enumerated above, both domestic and foreign, areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns the construction of a snowmobile. Morespecifically, the present invention concerns, first, a method for thedesign, construction, and assembly of platform for a snowmobile and,second, the platform made according to that method.

2. Description of the Related Art

The basic platform for a conventional snowmobile includes threecomponents, a tunnel at the rear of the snowmobile, an engine cradleconnected at the front of the tunnel, and a front suspension connectedto the engine cradle. The three components are integrally connected toform a unitary structure that is rigid enough to withstand the forcesimpingent thereupon during operation of the snowmobile.

In the conventional snowmobile, the tunnel is disposed above an endlesstrack that propels the vehicle. The engine cradle is the structuralportion of the platform that extends forwardly from the tunnel andsupports the engine near the front of the vehicle. The front suspensionis the structural component integrated as a part of the engine cradle,located to the sides of the engine cradle. The steering skis aresuspended from the front suspension, which includes shock absorbers thatdampen the forces encountered by the skis as the vehicle travels overeither groomed or rough terrain.

FIG. 1 illustrates the construction of one conventional snowmobileplatform 10. The tunnel 12 and the engine cradle 14 are depicted in thisillustration. The tunnel 12 forms the rear portion of the platform 10while the engine cradle 14 forms the forward portion of the platform 10.

The tunnel 12 is essentially an inverted, U-shaped element. The tunnel12 has a top portion 16, a left side portion 18, and a right sideportion 20. A left side foot board 22 extends outwardly from the leftside portion 18 of the tunnel 12. A right side foot board (not shown)similarly extends outwardly from the right side portion 20 of the tunnel12.

The rear end 24 of the engine cradle 14 is attached at the front end 26of the tunnel 12. The engine cradle 14 includes a bottom pan 28, a leftside wall 30, a right side wall 32, a front portion 34, and a rearportion 36. Together, the bottom pan 28, the left side wall 30, theright side wall 32, the front portion 34, and the rear portion 36 createa rigid structure onto which the engine for the snowmobile is secured. Astructural upright 38 is connected adjacent to the rear portion 36 ofthe engine cradle 14. The upright 38 provides structural support for thehandlebar used to steer the snowmobile.

The tunnel 12 includes openings 40 through the left side 18 and throughthe right side 20. A drive shaft (not shown) passes through the openings40. The drive shaft operatively connects to the endless track positionedbeneath the tunnel 12 to propel the vehicle. The drive shaft alsooperatively connects to the engine (not shown), which sits above thebottom pan 28 of the engine cradle 14. As would be understood by thoseskilled in the art, motive power is transferred from the engine to theendless track via the drive shaft. The opening 40 in the left side 30 ofthe engine cradle 14 is also illustrated in FIG. 1. A similar opening(not shown) also passes through the right side 32 of the engine cradle14. The openings 40 in the engine cradle 14 and the openings 40 in thetunnel 12 lie in register with one another so that the drive shaftpasses through all four of the openings when the tunnel 12 and theengine cradle 14 are assembled together.

FIG. 2 illustrates one possible embodiment of the front suspension 42for a conventional snowmobile. While the details of the engine cradle 14in FIG. 2 differ slightly from those illustrated in FIG. 1, thoseskilled in the art would appreciate readily that the front suspension 42illustrated in FIG. 2 may be incorporated as a part of the platform 10illustrated in FIG. 1.

The left-hand side of the front suspension 42 is shown in FIG. 2. Aswould be appreciated by those skilled in the art, the right-hand side ofthe front suspension 42 is a mirror image of the left-hand side. Theleft-hand side of the front suspension 42 includes a ski leg 44 that isrotatably coupled to a lever arm 46. The lever arm 46, in turn, ispivotally connected to the engine cradle 14 via a structural pivot 48.The lever arm 46 pivots up and down as the snowmobile travels over theground.

The forward end 50 of the lever arm 46 includes a bracket 52 thatconnects to the lower end 54 of a shock absorber 56. The upper end 58 ofthe shock absorber 56 connects to a bracket 60 that is, in turn,connected to the engine cradle 14 at a location 62 near a forward endthereof. The shock absorber 56 dampens the forces encountered by the ski64 connected at the lower end of the ski leg 44.

As FIGS. 1 and 2 illustrate, the tunnel 12, the engine cradle 14, andthe front suspension 42 are integrally assembled to create a rigid frameonto which the remaining elements of the snowmobile are attached.

In the construction of the conventional snowmobile platform 10, thewidth of the tunnel 12 and the width of the engine cradle 14 areselected as a function of the width of the endless track that propelsthe vehicle. While engine size typically varies from one model ofsnowmobile to another, the width of the endless track, and therefore thewidth of the tunnel 12 and the engine cradle 14, typically remains thesame regardless of the size of the engine employed to propel thevehicle. This is because the width of the endless track typicallyremains the same for all types of snowmobiles.

There are several engine sizes typically incorporated into conventionalsnowmobiles, including 600 cc (cubic centimeters of displacement), 700cc, and 800 cc varieties, for example. To accommodate each of theseengine sizes, the front suspension 42 and the tunnel 12 of each platformdiffers from one vehicle to another. The front suspensions 42 differbetween vehicle types to accommodate the variations in weight of thedifferent engines. As a general rule, the larger the displacementvolume, the heavier the engine. Therefore, the front suspension needs tobe more robust. The tunnels 12 vary from one vehicle to another toaccommodate different lengths of the endless track.

While the width of the endless track typically remains the same, thelength of the endless track can vary from one snowmobile type toanother. For a racing snowmobile, which is designed primarily forgroomed surfaces, the endless track typically is shorter than theendless track incorporated into a mountain snowmobile, which is designedto operate in ungroomed (or powder) snow. Accordingly, the tunnel 12 fora racing snowmobile is generally shorter than the tunnel 12 for amountain snowmobile. In addition, the weight of a racing snowmobile isof critical concern because unnecessary weight slows the vehicle, whichis antithetical to racing.

Once the platform 10 for the vehicle is designed, the chassis for thesnowmobile is designed around it. As with the platform 10, the chassisis designed to accommodate variation in the components of the vehicle.

To manufacture each new vehicle type, whether it is a racing snowmobile,a mountain snowmobile, or a hybrid variety, considerable engineering andmanufacturing resources are required. Each new vehicle must be designedfrom the ground up. From an engineering standpoint, therefore, each newvehicle consumes a significant number of engineering hours because theplatform 10 of the vehicle has to be designed from scratch. In addition,from a manufacturing standpoint, each new vehicle consumes a significantnumber of training hours, because the technicians responsible forassembling the vehicle must be trained to understand the construction ofeach new vehicle so that the vehicle may be assembled properly on theassembly line. The design and manufacture of a conventional snowmobile,therefore, is inherently inefficient both from a design and from amanufacturing standpoint, because there is a considerable duplication ofeffort for each new vehicle that is designed and manufactured.

Accordingly, the inefficient method of designing and manufacturingconventional snowmobiles cries out for a solution.

The prior art does not provide a solution for this inefficiency.

SUMMARY OF THE INVENTION

Recently, Bombardier Inc. (Bombardier) of Montreal, Quebec, Canada, aleading producer of snowmobiles, redesigned its snowmobile in responseto consumer demand and in an effort to update the design andconstruction of the vehicle. While designing its new vehicle, Bombardierreexamined the traditional design and manufacturing of snowmobiles toaddress the inefficiencies enumerated above.

As will be made apparent in the discussion that follows, the new designselected by Bombardier for its new snowmobile led to a departure fromtraditional design and manufacturing techniques and, as a result, led tothe development of the present invention.

Among other aspects and benefits, the present invention provides a novelengineering and manufacturing method for the construction of asnowmobile platform that resolves many of the inefficiencies identifiedwith the design and manufacturing of traditional snowmobile platforms.

In particular, it is one aspect of the present invention to provide amethod of designing and manufacturing snowmobile platforms where thecost associated with the design and manufacture of the platform isgreatly reduced by comparison with the traditional design andmanufacturing technique.

Another aspect of the present invention provides a standardized designfor a snowmobile platform.

Still another aspect of the present invention provides a snowmobileplatform that is modular in design. Among other things, the modulardesign accommodates variation between individual platforms whilemaximizing interchangeability of platform components.

Among other aspects, the present invention provides for a method ofassembling a snowmobile platform. The method entails designing andmanufacturing a group of tunnel subassemblies comprising at least twotunnel subassemblies. In addition, the method includes designing andmanufacturing a group of engine cradle subassemblies comprising at leasttwo engine cradle subassemblies and designing and manufacturing a groupof front suspension subassemblies comprising at least two frontsuspension subassemblies. Next, one tunnel subassembly from the group oftunnel subassemblies, one engine cradle subassembly from the group ofengine cradle subassemblies, and one front suspension subassembly fromthe group of front suspension subassemblies are selected. Then, thetunnel subassembly is connected to the engine cradle subassembly at arear portion thereof. Finally, the front suspension subassembly isconnected to the engine cradle subassembly at a front portion thereof tocreate the snowmobile platform.

Another aspect of the present invention is the provision of a snowmobileplatform. The platform includes a tunnel subassembly selected from agroup of tunnel subassemblies. It also includes an engine cradlesubassembly, selected from a group of engine cradle subassemblies,attached forwardly of the tunnel subassembly. The platform also includesa front suspension subassembly, selected from a group of frontsuspension subassemblies, attached forwardly to the engine compartmentsubassembly.

Other aspects of the present invention will become apparent from thediscussion that follows.

DESCRIPTION OF THE DRAWINGS

Throughout the description of the present invention, reference to commonelements will be made using the same reference numbers, in which:

FIG. 1 is an exploded, perspective illustration of a platform of a priorart snowmobile, illustrating the tunnel and engine cradle that form apart of the platform;

FIG. 2 is an exploded perspective illustration of the front suspensionsubassembly for the platform of a prior art snowmobile, such as theplatform illustrated in FIG. 1;

FIG. 3 is a perspective illustration of the snowmobile that provided theimpetus for the teachings of the present invention;

FIG. 4 is a perspective illustration, from the left, rear side, of thesnowmobile platform from the snowmobile illustrated in FIG. 3;

FIG. 5 is a schematic illustration of the relative dimensions associatedwith the basic elements of the snowmobile platform constructed inaccordance with the teachings of the present invention;

FIG. 6 is a schematic illustration of several variations for the frontsuspension subassembly for the snowmobile platform designed andmanufactured according to the teachings of the present invention;

FIG. 7 is a schematic illustration of several variations for the enginecradle subassembly for the snowmobile platform designed and manufacturedaccording to the teachings of the present invention;

FIG. 8 is a schematic illustration of several variations for asnowmobile platform, emphasizing the interchangeability of the platformcomponents in accordance with the teachings of the present invention;and

FIG. 9 is a schematic illustration of several additional variations forthe snowmobile platform designed and manufactured according to theteachings of the present invention, showing two groups of possiblevariants of the platform, each of which share a common tunnelsubassembly.

DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION

FIG. 3 illustrates one possible embodiment of a snowmobile 100 designedand constructed in accordance with the teachings of the presentinvention. The snowmobile 100 has a front end 102 and a rear end 104.The front end 102 is provided with one or more fairing elements 106,including a bottom pan 108, a side panel 110, and a motor cover 112 Aswould be understood by those skilled in the art, the front end 102 ofthe snowmobile 100 houses the engine (not shown) beneath the fairingelements 106. A front suspension 114 is connected at the front end 102of the snowmobile 100. As with the prior art snowmobile, two skis 116are suspended from the front suspension 114.

The endless track 118 that is operatively connected to the engine isdisposed beneath the rear end 104 of the snowmobile 100. A seat 120 ispositioned generally above the endless track 118. A windshield 122 isdisposed atop the fairing elements 106 at the front end 102 of thesnowmobile 100. A handlebar (not shown) is positioned behind thewindshield 122. The handlebar is operatively connected to the skis 116so that the snowmobile 100 may be turned during operation.

The front suspension 114 of the snowmobile 100 differs from the frontsuspension 42 on the prior art snowmobile illustrated in FIGS. 1 and 2in at least one significant respect. In particular, the front suspension114 is a double A-arm suspension, much like the type of suspensionincorporated into automobiles. Shock absorbers 124 connect between theA-arms 126 of the front suspension 114 and the frame of the snowmobile100 to dampen the forces experienced by the snowmobile 100 duringoperation.

FIG. 4 illustrates, from the rear left side, the platform 128 designedfor the snowmobile 100 illustrated in FIG. 3. The platform 128 includesa tunnel subassembly 130 with a rear end 132 and a front end 134. Thetunnel subassembly 130 comprises an inverted U-shaped tunnel 136 havinga top portion 138 and left and right sides 140, 142 extending downwardlyfrom the top portion 138. A left footboard 144 extends outwardly fromthe bottom of the left side 140 of the tunnel 136. Similarly, a rightfootboard 146 extends outwardly from the bottom of the right side 142 ofthe tunnel 136. A radiator 148 is incorporated into the top portion 138of the tunnel 136 and is a part of the tunnel subassembly 128illustrated in this figure. The radiator 148, which fluidly connects tothe engine to cool the engine, is positioned to receive snow thrownthereupon by the endless track 118 positioned beneath the tunnel 136.

FIG. 4 also illustrates another aspect of the tunnel 136. In particular,the tunnel 136 has a left-hand portion 141 and a right-hand portion 143.As illustrated, the left-hand portion 141 and the right-hand portion 143are connected to either side of the radiator 148. So constructed, theleft-hand portion 141 and the right-hand portion 143 may be separatedfrom the radiator 148 and replaced with wider or narrower replacementsto widen or narrow the width of the tunnel 136.

As would be appreciated by those skilled in the art, the radiator 148need not be included in the tunnel 136. If the radiator is omitted, theleft-hand portion 141 and the right-hand portion 143 would join oneanother at a seam roughly at the center of the tunnel 136. With such aconstruction, the left-hand portion 141 could be separated from theright-hand portion 143 so that the two portions could be replaced withwider or narrower left-hand and right-hand portions 141, 143.Accordingly, the width of the tunnel 136 could be made wider or madenarrower, depending upon the width required for the platform 128.

An engine cradle subassembly 150 connects to the front end 134 of thetunnel subassembly 128. The engine cradle subassembly 150 includes,among other elements, a bottom pan 152, a left wall 154, a right wall156, a front wall 158, and a rear wall (not shown). An opening 160 isdisposed through both the left wall 154 and the right wall 156 of theengine cradle assembly 150. The drive shaft (not shown) of thesnowmobile 100 extends through the opening 160. The drive shaft connectsbetween the engine and the endless track 118 to transmit motive powerfrom the engine to the endless track 118.

As FIG. 4 illustrates, the left side wall 154 and the right side wall156 of the engine cradle subassembly 150 do not need to have the sameconstruction. In particular, the left side wall 154 has an openconstruction, which permits ready access to the engine placed within theengine cradle subassembly 150. The right side wall 156, on the otherhand, has a closed construction that reflects heat generated by theengine back into the engine cradle subassembly 150. Accordingly, theright side wall 156 helps to manage heat losses from the engine duringoperation of the snowmobile. Other constructions for the left side wall154 and the right side wall 156 are also possible, including a closedconstruction with removable sections to facilitate access to the enginewhen the engine is maintained or serviced.

In another embodiment, it is contemplated that the tunnel subassembly130 and the engine cradle subassembly 150 may be manufactured togetheras an integral component of the platform 128. If so manufactured, theleft side 140 of the tunnel and the left wall 154 of the engine cradlecould be manufactured as a single, unitary left side wall. The rightside 142 and the right wall 156 could be similarly combined. If theplatform 128 were to be constructed in this fashion, the left-hand walland the right-hand wall would extend the entire length of the enginecradle subassembly 150 and the tunnel subassembly 130.

As shown in FIG. 4, a front suspension subassembly 162 is connected toand extends forwardly from the engine cradle subassembly 150. The frontsuspension subassembly 162 includes a V-shaped member 164 that isattached to the engine cradle subassembly 150. Right and left side walls166, 168 extend upwardly and are integrated with or connected to theV-shaped member 164. The shock absorbers 124 and two A-arms 126 extendoutwardly from either side of the front suspension subassembly 162 tosupport the skis 116 on either side of the snowmobile 100.

An upper frame subassembly 170 is connected to the platform 128 abovethe tunnel subassembly 130, the engine cradle subassembly 150, and thefront suspension subassembly 162. The upper frame subassembly 170provides additional structural rigidity to the platform 128. The upperframe subassembly 170 includes two rear supports 172, a middle support174, and two forward supports 176. Together, the rear supports 172,middle support 174, and forward supports 176 for a pyramid-shapedstructure that is connected to the tunnel subassembly 130, the enginecradle subassembly 150, and the front suspension subassembly 162.Alternatively, the middle support 174 may be omitted, where appropriate.The upper frame subassembly 170 defines an apex 178, which supports thesteering handlebar for the snowmobile 100.

The construction of the platform 128 differs from the platform 10 of theprior art in at least one significant respect. In particular, theplatform 128 is designed and constructed so that the front suspensionsubassembly 162 connects to the front of the engine cradle subassembly150. For the prior art platform 10, the front suspension 42 waspositioned beside or beneath the engine cradle 14, was housed by theengine cradle 14, or was constructed as a part of the engine cradle 14.

The change in the construction of the snowmobile 100 to combine thetunnel subassembly 130, the engine cradle subassembly 150, and the frontsuspension subassembly 162 together to construct the platform 128illustrated in FIG. 4 provides numerous advantages, one of whichresulted in the development of the present invention.

In particular, the present invention capitalizes upon the fact that theplatform 128 is designed and constructed from the tunnel subassembly130, the engine cradle subassembly 150 and the front suspensionsubassembly 162. In addition, the present invention also capitalizes onthe split construction of the tunnel 136, which has left-hand portions141 and right-hand portions 143 with a varying width. With such aconstruction, it is possible to mix and match components to accommodatedifferent riding styles of snowmobiles, a construction methodologypreviously unavailable to the snowmobile manufacturer.

FIG. 5 illustrates the basic design and construction concept thatunderlies the present invention. In particular, the connection of atunnel assembly 180, an engine cradle subassembly 182, and a frontsuspension subassembly 184 is illustrated. The three subassemblies areconnected in the same order as the platform 128 illustrated in FIG. 4 tocreate a platform 198. Since these subassemblies may not share the samestructural components as the platform 128, different reference numbersare being used to identify these subassemblies.

As illustrated in FIG. 5, the tunnel subassembly 180 has a length 186and a width 188. Similarly, the engine cradle subassembly 182 has alength 190 and a width 192. The front suspension subassembly 184 alsohas a length 194 and a width 196. The width of the platform 198 isdefined by the largest width of the three subassemblies 180, 182, 184.In this particular example, the width 188 of the tunnel subassembly 180defines the greatest lateral dimension for the platform 198. It isexpected that the tunnel subassembly 180 typically will be the widest ofthe three components. However, given the variability that the presentinvention offers, this need not always be the case.

FIG. 6 illustrates schematically for different front suspensionsubassemblies: (1) a small platform front suspension subassembly 200,(2) a large platform front suspension subassembly 202, (3) a deep snowfront suspension subassembly 204, and (4) a trail front suspensionsubassembly 206. Each of these front suspension subassemblies differfrom one another according to the riding conditions anticipated. Forexample, the large platform front suspension subassembly 202 will bestructurally more robust than the small platform front suspensionsubassembly 200.

FIG. 7 schematically illustrates four different engine cradlesubassemblies: (1) a small engine cradle subassembly 208, (2) a mediumengine cradle subassembly 210, (3) a large engine cradle subassembly212, and (4) an extra-large engine cradle subassembly 214. The smallengine cradle subassembly 208 is designed and constructed to support asmall engine, which includes a two-stroke, one-cylinder engine or a 277cc-FC engine, for example. The medium engine cradle 210 is designed andconstructed to accommodate a medium-sized engine such as a two-stroke500 cc-FC engine, a similar engine with a larger displacement, or an LCengine with up to an 800 cc displacement, for example. The large enginecradle subassembly 212 is designed and constructed to accommodatelarge-sized engines including, among other varieties, both two-strokeand four-stroke engines with a displacement of 995 cc and up. It is alsocontemplated that the large engine cradle subassembly 212 mayaccommodate an in-line, four-stroke engine. The extra-large enginecradle subassembly 214 is designed and constructed to accommodateextra-large engines including, for example, a four-stroke, V-type 400 ccengine, a four-stroke, V-type 1400 cc engine, or an engine of the samesize with a displacement between 400 cc and 1400 cc.

As would be understood by those skilled in the art, the specific enginevarieties identified above are meant to be illustrative of the types ofengines contemplated for placement into the particular engine cradlesubassembly mentioned. The engines listed, however, are not meant tolimit the invention. It is contemplated, for example, that a smallengine cradle subassembly 208 may accommodate any other type of enginetherein. Moreover, the designations “small,” “medium,” “large,” and“extra-large” are meant to be illustrative of the variety of enginecradle subassemblies that may be designed and constructed according tothe teachings of the present invention.

Two specific examples of different engine cradle subassemblies areprovided below for illustrative purposes. As indicated above, theseexamples are meant to be illustrative only and are not meant to limitthe scope of the present invention.

Engine Cradle Subassembly for a Two-Stroke 600 cc Engine Width 44 inchesLength 40 inches Depth 20 inches Sides one side open, one side closedFront Engine Mounts 2 vertical rubber mounts Rear Engine Mounts 2vertical rubber mounts

Engine Cradle Subassembly for a V-Type 1000 cc Engine Width 48 inchesLength 44 inches Depth 30 inches Sides both sides closed Front EngineMounts 2 horizontal rubber mounts Rear Engine Mounts 2 vertical platerubber mounts

As illustrated in FIG. 8, the tunnel subassembly 180 also may bedesigned and constructed to have a variety of widths 188 and lengths186. For example, a short tunnel subassembly 216 is contemplated for usewith a small snowmobile, such as a racing vehicle. Conversely, a longtunnel subassembly 218 is contemplated for use with a mountainsnowmobile, for example.

As the foregoing should make apparent, there can be considerablevariation from one type of each of the three subassemblies to another.Accordingly, the method for the design and construction of a snowmobileplatform of the present invention involves the following. First, amultiplicity of tunnel subassemblies are designed and constructed tomeet predetermined structural and operating characteristics. Second, anumber of engine cradle assemblies are designed and constructed to meetpredetermined structural and operating characteristics. Third, a numberof front suspension subassemblies are designed and constructed to meetpredetermined structural and operating characteristics. Next, one fromeach of the tunnel subassemblies, engine cradle subassemblies, and frontsuspension subassemblies are selected. The three selected subassembliesare then assembled together to form a platform for a particularsnowmobile. Then, where additional frame rigidity is deemed appropriate,an upper frame subassembly is attached to the completed platform. Onceassembled, the remaining components of the snowmobile are assembled ontothe platform.

FIG. 8 provides one example of the variability of the design andmanufacturing method of the present invention. In the example providedin FIG. 8, the front suspension subassembly is selected as a constantvariable in the construction of a platform 220. As illustrated, thetrail front suspension subassembly 206 has been selected. Fourvariations on the platform 220 are illustrated. The first variationincludes a medium engine cradle subassembly 210 to accommodate atwo-stroke 400 cc direct injection internal combustion engine. Thatengine cradle subassembly 210 is then combined with a short tunnelsubassembly 216, which is common for a small snowmobile used for racing,for example. The second variation combines the trail front suspensionsubassembly 206 with the medium engine cradle subassembly 210 and a longtunnel subassembly 218, such as that commonly provided for a mountainsnowmobile. The third variation combines the trail front suspensionsubassembly 206 with the extra-large engine cradle subassembly 214capable of accommodating a four-stroke, V-type, 855 cc internalcombustion engine. A short tunnel subassembly 216 is connected to thesecomponents to from the platform 220. The fourth variation combines thetrail front suspension subassembly 206 with the extra-large enginecradle subassembly 214 and the long tunnel subassembly 218.

FIG. 9 illustrates other variations in the construction of a platform222. In this example, the tunnel, which is selected as a long tunnelsubassembly 218, is combined with any of the engine cradle subassemblies208, 210, 212, 214 and front suspension subassemblies 200, 202, 204, 206as may be appropriate for the snowmobile being created.

As would be appreciated by those skilled in the art, the permutationsavailable for the construction of a snowmobile platform using just thecomponents listed above is considerable. With two tunnel subassemblyvariations, four engine cradle subassembly variations, and four frontsuspension subassembly variations, there are thirty-two differentplatforms that may be created. Naturally, if the number of tunnelsubassemblies, engine cradle subassemblies, and front suspensionsubassemblies designed and constructed as a part of the group ofpotential subassemblies is increased, the number of variations inplatforms can be increased further still.

With this in mind, the snowmobile manufacturer may decrease, in someinstance greatly decrease, the cost associated with the design andconstruction of snowmobile platforms. Rather than designing eachplatform from scratch for each new snowmobile, which has been thepractice in the prior art, the snowmobile manufacturer needs only designand construct one of the three subassemblies needed for the new vehicle.The remaining two subassemblies for the platform may be chosen fromfront suspension subassemblies and tunnel subassemblies previouslydesigned. In addition, manufacturing costs may be reduced, because theknowledge and training required for assembly line professionals may bereduced. Other advantages also may be realized by practicing the presentinvention.

The embodiments of the present invention that are described above aremeant to be illustrative of the present invention only. The embodimentsillustrated and described are not meant to limit the present inventionsolely to the embodiments described. Those skilled in the art wouldreadily appreciate the unlimited potential of the present invention.

1. A method of assembling a snowmobile platform, comprising: providing agroup of front suspension subassemblies, the group of front suspensionsubassemblies including at least two front suspension subassemblieshaving different characteristics; providing a group of engine cradlesubassemblies, the group of engine cradle subassemblies including atleast two engine cradle subassemblies having different characteristics,each of the engine cradle subassemblies of the group of engine cradlesubassemblies being connectable to each of the front suspensionsubassemblies of the group of front suspension subassemblies; providinga group of tunnel subassemblies, the group of tunnel subassembliesincluding at least two tunnel subassemblies having differentcharacteristics, each of the tunnel subassemblies of the group of tunnelsubassemblies being connectable to each of the engine cradle of thegroup of engine cradle subassemblies, forming a snowmobile platform atleast in part by combining a front suspension subassembly selected fromthe group of front suspension subassemblies, an engine cradlesubassembly selected from the group of engine cradle subassemblies and atunnel subassembly selected from the group of tunnel subassemblies. 2.The method of assembling a snowmobile platform of claim 1, furthercomprising: forming the tunnel subassembly and the engine cradlesubassembly integrally as a single component.
 3. The method ofassembling a snowmobile platform of claim 1, further comprising:attaching the engine cradle subassembly to the tunnel subassembly. 4.The method of assembling a snowmobile platform of claim 1, wherein: thegroup of tunnel subassemblies includes a short tunnel subassembly and along tunnel subassembly.
 5. The method of assembling a snowmobileplatform of claim 1, wherein: the group of engine cradle subassembliesincludes at least two from a group comprising a small engine cradlesubassembly, a medium engine cradle subassembly, a large engine cradlesubassembly, and an extra-large engine cradle subassembly.
 6. The methodof assembling a snowmobile platform of claim 1, wherein: the group offront suspension subassemblies includes at least two selected from agroup comprising a small platform front suspension subassembly, a largeplatform front suspension subassembly, a deep snow front suspensionsubassembly, and a trail front suspension subassembly.
 7. The method ofassembling a snowmobile platform of claim 1, further comprising:connecting an upper frame subassembly to at least two of the tunnelsubassembly, the engine cradle subassembly, and the front suspensionsubassembly.
 8. The method of assembling a snowmobile platform of claim1, wherein the selected tunnel subassembly comprises: a top with leftand right sides, a left side wall extending downwardly from the leftside of the top, and a right side wall extending downwardly from theright side of the top, such that the selected tunnel subassembly formsan inverted U-shaped tunnel.
 9. The method of assembling a snowmobileplatform of claim 8, wherein: a width of the tunnel subassembly isselected at least as a function of a width of an endless track selectedfor attachment to the snowmobile platform; and a length of the tunnelsubassembly is selected at least as a function of a length of theendless track selected for attachment to the snowmobile platform. 10.The method of assembling a snowmobile platform of claim 1, wherein theselected engine cradle subassembly comprises: a bottom pan with left,right, front, and rear sides; a left side wall attached to the left sideof the bottom pan; a right side wall attached to the right side of thebottom pan; a front wall attached to the front of the bottom pan; and arear wall attached to the rear of the bottom pan.
 11. The method ofassembling a snowmobile platform of claim 10, wherein: the width of theengine cradle subassembly is selected at least as a function of a sizeof an engine selected for placement onto the snowmobile platform; andthe length of the tunnel subassembly is selected at least as a functionof the size of the engine selected for placement onto the snowmobileplatform.
 12. The method of assembling a snowmobile platform of claim 1,wherein the selected front suspension subassembly comprises: a V-shapedmember with left and right sides; a left side wall attached to the leftside of the V-shaped member; a right side wall attached to the rightside of the V-shaped member; at least four A-arms pivotally connected tothe V-shaped member, two on the left side and two on the right side; atleast one shock absorber connected between the left side wall and one ofthe A-arms on the left side of the V-shaped member; and at least oneshock absorber connected between the right side wall and one of theA-arms on the right side of the V-shaped member.